Furnace construction



May29,1'945. l c. VARRQLL 2,317,210

.FURNACE CONSTRUCTION Filed Aug. 7, 1944 s sneets-sneet' 1 C@ ttor-ngs.

May 29', 1945. fc. V.. CARROLL EURNAE CONSTRUCTION taken Patented May UNITEDv STATES PATENT oFFlcE FURNACE CONSTRUCTION Charles V. Carroll, Minneapolis, Minn., assignor to Wm. Bros Boiler & Manufacturing Co., Minneapolis, Minn., a corporation of Minnesota Application August 7, 1944, Serial No. '548,400

('Jlaims.l (Cl. 11o-39) This invention relates to furnace and boiler grate constructions-and particularly to furnaces and boiler constructions'wherein there is utilized a shaker grate mechanism and positive feed of combustion air under the grate lip pressure, in-

duced draft or natural draft. In furnaces and boilers of such construction and design there occurs the problem of maintaining control of the under grate air against leakage loss or air inflow (depending upon whether a, positive or negative pressure exists under the grate) and also the problem of providing. a hand or power mechanism for communicating powerto the grates forgrate shaking operations. Mechanisms heretofore provided for these purposes have not been entirely satisfactory due to air leakage, di'iculty of maintenance, and inadequate -power transmission to the grates, the latter diiculty being a problem particularly where clinkering coal is burned.

.It is an objectof this invention to overcome these inadequacies of prior furnace constructions .and to provide a strong, adequately powerful,

Y those inherent in the apparatus herein illustrated,

` described 'and claimed.

The invention is illustrated in the drawings in which Y Figure l is a fragmentary side elevational view,` partly in section, of the apparatus of the invention showing the grates in level grate position;

Figure- 2 is a view corresponding to that shown in Figure 1 except Ythat the grates are shown in the dumping position;

Figure 3 is a 'fragmentary cross sectional view Y 'taken along the line 3-3 of Figure 1. In Figure 3 lthe section line I--I is the line on whichr the sectional views shown in Figuresl and 2 are Figure 4 is a fragmentary sectionalV view taken along the linevl-l of Figure 2; and l Figure 5 is a fragmentary sectional view taken along the line 5--5 of Figure 1`. y

Throughout the drawings corresponding nu merals indicate identical parts.

ture includes foundation generally designated I0 having downwardly sloping ash pit'iioor I I. 'I'he foundation includes an air inlet which enters through one wall of the ash pit or plenum chamber, here illustrad bythe duct opening I2 in the back wall of the furnace illustrated by the refractory lining I3. 'I'he refractory lining is provided with an air duct I4 so as to introducefrom the air duct I2 a small amount of air above the fire via arrow I5.

' The under-grate air plenum space may operate under positive or negative pressure depending upon whether natural, induced or forced draft is used-but in any event the volume of air supplied to the under side of the grate must be controlled carefully, thus requiring that leakage be minimized, so thatV suitable damper control will be eiective. The'grate surfaces vare supported upon side rails and cross frame members. In this instance the grate is a double gratef and having a middle pier of the foundation at I6 and side walls of the foundation at II and I8. t Upon the side walls Il and I8 are grate side frame members 20 and 2I and upon the middle pier I6 there are placed back-to-back a similar pair ofside frame members 22 and 23.

The side frame members 20 and 2I are provided with cap 'pieces 26 and 21 which are shaped so as to provide the outwardly sloping surfaces at 28 and 29 so as to serve on the sides to retain the solid fuel bed burned on the grate. 'Ihe surfaces 28 and 29 are provided with apertures 30 and 3|, respectively, through which 'combus- `tion air is introduced. The grate side frame members 22 and 23 supported upon the middle pier are likewise provided withcaps 34' and 35, respectively, of somewhat diiferent design, shaped 'so as to present a level grate surface equal to that afforded by the grate bars hereinafter described. It is to be understood, of course, that the cap grates 34 and 35 form an immovable tier along the center of the grate area.

The side frame members 2li-22 and A2I-23 are held together at their ends by cross frame members. there is illustrated a` front cross frame member 3i which is suitably supported on the foundation and is attached to the side frame members, in this instance members 2I and 23. The front cross frame member is provided with a grate area indicated under the bracket 31 which has an irregular upper surface and is provided with air slots 38. An overhanging front ange v39 on the cross frame member is spaced from the main body Referring to the drawings, the furnace struc- 55 0i the cross frame member so as to provide a re- Thus, referring to Figures 1 .and 2 cess into which one flange et of the channel 'Lil is adapted to t.` The channel il serves aspart Upon the cross frame member il@ there is positioned a cap member generally designated 52 which is provided with air inlet openings 53 for supplying combustion air to the solid fuel whichA beds against the cap. It will be noted that an air space is provided at tl between the rear wall formed by the cross frame member 113 and a portion of the cap 52 and the machinery of the rear of the furnace illustrated at i3. It is to be understood that similar front and back cross frame members are provided for as many of the pairs of the side frame members as are included in the grate area. Thusanother pair of front and back?. cross frame members are provided for the side frame members 2i] and 22 and in the event the grate area is three or more tiers wide additional units are installed.

The side frame members 2Q and 22 (also 2l and 23) are provided with U-shaped bearing notches illustrated at 5t and 5l in Figures l and 2, the bearing notches on opposite side frame members being so positioned as to be directly on a line transversely across the grate area. in larger furnaces, longer side frame members are tted to receive a larger number of carrier bars. |The bearing notches have a conical bottom surface as `illustrated at Sil, V59, t@ and @l in Figure 3, and into the bearing notches there are received the stub end shafts of the carrier bars generally desig nated t5.

Referring to Figures l-3 the carrier bars have an intermediate portion indicated by the bracket 56 having a cross section similar to that of a railroad rail in that it has an approximately rectanguiar head portion till, a web t and a bottom flange 69. On the ends of this intermediate section there are provided the stub shafts lll and ll which have a cylindrical under surface generated about an axis at the level of point lB-ll. The portion of the stub shaft which is level with the top of the head portion 6l of the intermediate section is flattened olf, inasmuch as it does not form a portion ofthe bearing surface in normal operation. The stub end shafts 'it and ll contact the somewhat conical surfaces 58 and 59 of the bearing notches in what approaches a line contact and therefore air freely moves around the ends of the shafts and prevents overheating. It

i 3l. The ow of air thus around the ends of the stub shafts tends to keep them cool during operation and prevents burning ofi. The intermediate section of the carrier bar is provided with a downwardly extending carrier bar lever which isadequately side braced by gussets 1S. It will be understood that the lever 15 and gussets 76 are cast integral with the intermediate section 66 of the carrier bar and that the stub shafts 1li and 1I are likewise integral. The bottom end of each of the carrierbar levers 15 is apertured at 18 vto receive a tie bar 'I9 which is held in place by pivot IBO asvaaio pins lit, the length of the carrier bar l@ and the position of the pivot connections to it being such that all of the carrier bars are held in the same relative angular position. At the forward end of the tie bar there is a downwardly protruding portion SE which is apertured to receive a pivot pin 33 upon which there is connected the shaker link @il extending to the-lever member generally designated 9i?.

On the intermediate portion 66 of each carrier bar there are placed a plurality of grate bars generally designated 36 of identical construction. The grate bars are preferably of a shape and configuration as shown in my copending application Ser. No. 548,399, entitled Shaker grate construction, filed concurrently herewith. The grate bars preferably have a top design such as shown and claimed in my copending application Ser. No. 548,398, entitled Gratef filed concurrently herewith. Since the grate bar design per se does not form a part of the present invention, they will not be further described but reference is made to the aforesaid applications which are incorporated herein by reference.

Upon the front wall of the ash pit there is mounted a panel :B3 which is held in place by a plurality of bolts b9. The panel 38 is provided with spaced parallel walls @l and 92 which lie in planes perpendicular to the axis of rotation of the carrier bars t5. The walls 92 present an open space along the line 93 and extend through the plane of the ash pit front wall 88 and extend through the plane of the front panel rearwardly to the ash pit and terminal at line 9d. The space between the walls @l and 92 is open to the ash pit space except that the walls are fastened together at the top, as illustrated at 95 and also fastened together across the bottom by a cylindrical web @tl which is generated about the axis of pivot 96 as a center. The walls 9i and 92 are apertured to receive a pivot pin 9B which serves as a pivotal axis for the lever member generally desig-A nated all.

The lever member S0 is of sufcient thickness so as neatly to lit into the space between the opposed surfaces of walls Sl and 92 and although it is :free to move arcuately therein'about the pivot pin Sb, the t is suiiiciently close to preclude any detrimental outow of the under fire combustion air around the lever 90. By the same token the lower surface 99 of the lever 99 is curved about the axis of pin 95 as a center and is of a dimension such that it neatly iits the inner surface of the web 983, thus sealing off the air ow at this point. The upper portion of the lever 9B illustrated'at lill is provided with a curved surface likewise generatedabout the axis of pivot pin 9@ so as to lit the correspondingly curved portion l @32 of the frame 95, thus serving to seal off the ow of air at this point. Thus, the lever 98 seals olf the air iiow between the walls 9| and 92 and the arcuate surfaces 98 and H32, regardless of the position of the lever 90.

The lever 9!! is provided with a hollowed out portion w3 into which the link 84 extends and is attached to the lever by means of the pivot pin 65. 'Ihe length of link 84 is such that the grates 86 are in the, level position (and the carrier bar operating levers 15 are in the vertical position), the lever 90 is in the position shown in Figure l, viz., extended forwardly to its forward limit of motion, as is' determined by the abutmentof the shoulder |06 of the lever 90 against a corresponding surface of the frame member 88. The lever 90 is provided with a socket |08 for reof double arrow l I Il. The motion is communicated through pin. M to link u, pin 83 and thence to the tie bar 19 and through the two edges of the carrier bar levers 15 that are connected to the tie bar. It i's to be understood that while only two carrier bars B5 are illustrated, more or less may be used, as desired. When the lever |09 isy moved to its lowermost position, shown in Figure 2 the tie bar 19 is moved to the position in which it is engaged by the downwardly ro tatedA forward end lli of certain of the grate bars 86, this being the limit of motion,

`Due to the fact that in the level grate position the link 84 maintains the lever 90 to its extreme forward position of rotation, shown in Figure 1, the link 84 is thereby brought nearer the axis of pin 9B than at any other place in the motion of the grate shaln'ng mechanism. Thus, the dimension D, which is the length of the normal line from the center of pin 98 to thl center line of link 84, is a minimum when the l grate mechanism` is inthe position shown in Figure l, and is a maximum in the position shown in Figure 2. Accordingly, the force 4multi-plica'- tion of the leverage consisting of shaker handle y I 09, lever 90 and link 84 is greatest when the grate is in the level position, or justleaving the level position, and accordingly a greater force is available in such positions for breaking loose clinkers or ash that may be caked on the grate surfaces: This is a distinct advantage inasmuch as the greatest force is needed when initiating the grate shaking operation. Once the encrusted ash and clinkers are broken loose the shaking operation is much easier than at the start of the shaking operation. Throughout the shaking operation, with the Vshaker mechanism and grates in any position, the out flow of under grate combustion air is prevented by the continuous close clearances that are maintained between the lever SII and the appropriately shaped enclosing walls of the frame 88. In this way the escape of combustion air, which is maintained under pressure under the grate, is prevented at all times.

As many apparently Widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the speciiic embodiments herein except as defined by l ing a shaker-type grate, an enclosed ashpit under said grate and means for supplying combustion posed to the outside of said ash pit wall for moving said sealing member.

2. An improved furnace construction comprising a shaker-type grate, an enclosed ashpit under the grate, means for supplying combustion air to the enclosed ashpit, a mechanical air lock means in the ashpit enclosure wall for communicating mechanical motion to the grate for shaking it without allowing air-now from the ashpit, including a pivot on the ashpit Wall, said wall having an opening adjacent to the pivot, a member pivotally mounted on said pivotl said member being shaped so as to cover the opening and to maintain contact with the ashpitv wall when ocillated back and forth on said pivot, means within the ashpit connecting the member and the shakerthe grate, means for supplying combustion air.

to the enclosed ashpit, a mechanical airlock means in the ashpit wall for communicating mechanical motion to the grate for shaking it comprising a member pivoted closely adjacent the ashpit wall and swingable on said pivot through the plane of the wall through an opening in said wall, said member and wall being iitted one to the other so as to seal the air against passage 'through said opening, and'mechanical connection means connecting said member and the grate for shaking movement of said grate when the member is oscillated on its pivot, and means connected to the portion of said member exposed to the exterior of the ashpit wall forv moving said member to and fro;

4. An improved furnace construction comprising a. shaker-type grate, an enclosed ashpit under the grate, means for supplying combustion air air thereto, mechanical air lock` means in the ashpit enclosing wall for communicating mechanical motion to the grate without allowing detrimental air iiow from the ashpit space, including a pair of spaced parallel walls extending' through said ashpit wall, said walls being connected by a. cylindrical segmental wall, a pivot to the portion of the movable sealing member ex- 'l5 adjacent the pivot,

to the enclosed ashpit, a mechanical air lock means in the ashpit wall for communicating mechanical motion to the grate for shaking it, said ashpit being provided with a pivot the axis of which is parallel to the wall of the ashpit, an opening through the ashpit wall and panels perpendicular to the ashpit Wall and to the axis of said pivot, a curved web connecting ysaid panels, said curved web being generated with the pivot as a center, an oscillating member mounted for swinging movement upon said pivot, said member being shaped to fill the space between said panels and between the ashpit wall and curved web so as to seal the ashpit against outflow of air, me`

.chanical means connecting the member and said shaker-type grate and means connected to that portion of the member exposed to the outside ofA the ashpit for swinging the member back andforth, Y

5. An improved furnace construction comprising a shaker-type-grate, an enclosed pit under 4the grate, means for supplying air thereto, said 4pit having a wall witha rectangular opening therethrough, enclosure walls extending parallel to each other and perpendicular to the vpit wall l on two sides of said opening, a. pivot mounted parallel/ to the plane of the wall along a third side .of the opening, a curved web fco'nnectin' V said enclosure walls, said ,web beinggenerated about the pivot as a center, a swinging member mounted on said pivot, said member being 'shaped so as to nt in substantial air-sealing relationship between the encmsure walls, the web and pit wan mechanical means connectlng seid swinging member and shaker grate end means connected to the portion of said swinging member exposed'to the exterior of the pit for swinging seid member.

S. The apparatus of claim 5 further characterized in that seid swing member has means to receive e shaker lever.

7. en improved furnace construction comprising grate carrier bor pivotally mounted for grate shaking oscillatory partial rotation around said pivots, en enclosed nit under seid grate and ineens for supplying eir thereto, said pit having e. vertical side wall, a, pivot mounted horizontally close to seid side Well and generally parallel to the pivote-i axis of seid grate carrier hars, e segment pivotelly mounted thereto'n swinging movement in a plane extending through the Dit side vieil, en opening through the pit side wall so as to permit said swinging movement, said pit side weil being iitted to said segment adjacent its pivot and et each side eno' at the bottom so es to Seel o air ow'therearound, a link; connecting the segment and grate carrier bei: and means connected tothe segment exteriorly o the pit for swinging seid segment.

3. The apparatus of cleini 'I further charecterizetl in that the linie is of such a length that the swing member is swung outward of seid pit when the gra-ttes ere in normal position.

9. The apparatus of claim 7 further characterized in. that the Segment has parallel side walls and e cylindrical segmental end portion.

lll. The epperetus of. claim l further eherec terized in that the segment has parallel side wells anti is cylindrioellv shaped at e smell diemet/er adjacent its pivoted end and cvlindricelly shaped about a large diameter et its opposite enel,

the ashpit Well. being extended so es to @merece the segment sidewalls and curved to t seid ier'ge end smell cylindrical portions of the side ive-ll. to 'eel it against sir outflow.

l.. .en improved furnace grote mechanism comprising carrier her extendingT across the grate aree, and pivotelly mounted. on its ends, e carrier har lever extending et an angle to the carrier ber airis, an intermediate lever pivotelly mounted on the furnace nit for swinging movement of the carrier har lever hach anal forth in e.'

direction transverse to the carrier her, a linl. connecting the carrier lever and the intermediate lever, seid link being of sueient length so es to hold the intermediate lever-sway from seid cerrier lever whereby the perpendicular diste-nce hetween the link end intermediate lever pivotal exis is less tnentheoistence between the intemedieteote lever pivotel arie, end the point of con= esmero nection of the link to saidintermediate lever, e. shelter handle xedly connected to the intera mediate lever.

l2. .en improved furnace grote construction comprising e. carrier ber having pivot ends extending on the level across the grote eres., pivotal mountings for the carrier her, e plurality of grote hars mounted on the carrier ber, seid carrier her having e cerrier bar lever extending downward therefrom when the grote bers ere in the level position, an intermediate lever pivotellv mounteel in spaced relationship transverseh7 with respect to the carrier ber, seid intermediate lever 'oef-.ng pivotally mounted upon en airis extending gener= elly perellel to the pivotal oi seid carrier he?, e.-

connecting seid osrrier her lever and said intermediate lever, saisi linl: being of enilcieot length so es to cause the intermediate lever to he rote-teo. evt/ev from. the carrier hor when. the letter is in normal position with the grate har level and the carrier har lever extending downward enti so es to bring the lint: closer to the "intermediate lever pivot then the diste-nce between sse-iol pivot and. the point of connection of the linl: to intermediate lever', enel shelter means connected to the intermediate lever. Y

i3. The apparatus o claim l2 further characterizeol in that there ere provided et leest one additional parallel carrier ber identical with first-mentioned carrier her, each seid. oa-r being pivotally mounted end having e downwardly extending carrier bar lever, and e, tie her pivote ally connected to each carrier bor lever so es to operate them in unison.

le. The apparatus of claim l2 further charac terized in that there are provided et least one additional parallel carrier bar identical with.

first-mentioned carrier har, eech seid. lier beine pivotelly mounted and having e. downwardly extending carrier bar lever enel e, tie ner is pivotelly connected to each carrier har lever so as te operate them in unison, and further chorect ized in that the link is nivotelhr connected t^ downwardly extending protuberence on the tie bar.

iti.- The apparatus of claim l2 further cheracterized in that the carrier har, grew here linie ere enclosed man eshpit into which corseI bustion air under pressure is forced, the intermediate lever being mounteolon the eshpit well for swinging movement through the plane of saisi wall, seid intermediate lever ond well heine' formed so es to air seal the lever with reference to the well to prevent outoiv of combustion air thereeround. 

